1. Field of the Invention
This invention relates to room temperature vulcanizable organopolysiloxane compositions. More particularly it relates to RTV organopolysiloxane compositions having improved shelf life and satisfactory curing and bonding properties for use as electric and electronic part adhesives.
2. Prior Art
A variety of room temperature vulcanizable (RTV) organopolysiloxane compositions are known in the art. Among these, organopolysiloxane compositions comprising a hydroxyl-endblocked organopolysiloxane, a curing agent such as methyltrimethoxysilane, and a catalyst such as an organic titanium compound or organic titanium chelate are widely used as adhesives in the electric and electronic industry fields. These compositions do not give off corrosives or stimulating odors because they cure into a rubbery organopolysiloxane while generating an alcohol.
These RTV organopolysiloxane compositions of the dealcoholysis type, however, have drawbacks of slow curing, poor internal curing and shelf stability. They often do not cure upon actual use after extended shelf storage, even under anhydrous conditions.
It is proposed to improve the curing properties and shelf stability of RTV siloxane compositions by adding thereto a silane compound having a dialkoxy group as a silane scavenger.
This method is successful in improving the shelf stability of RTV siloxane compositions only by substituting a reactive amide or amine group for a hydrolyzable group other than the dialkoxy group of the silane compound. Substitution of a reactive amide or amine group for a hydrolyzable group results in RTV siloxane compositions which generate toxic or corrosive gases upon curing, causing rust on the surface of a subject in contact therewith. Therefore, these compositions could not find application as adhesives in the electric and electronic industry fields.
Therefore, there is a need for a room temperature vulcanizable organopolysiloxane composition of quality having satisfactory curing properties and shelf stability.